The present invention relates to positive locking devices and in particular to positive locks for deployable whip antennas.
It is inherent in a whip antenna that one end is fixed and the other end is free. A common way of fixing one end of a whip antenna is to place the end in a ferrule and attach the ferrule to a socket that is in turn screwed into a mounting or otherwise immovably attached to a base. Such a technique is employed in U.S. Pat. No. 4,134,120, where the antenna element comprises a relatively inflexible composite rod.
Where the antenna element must be alternately stowed in a coiled configuration and deployed in an erect configuration, a common solution has been to wind the antenna element or its support on a drum which is attached to the fixed end of the antenna element and which limits its motion when deployed. U.S. Pat. No. 3,253,799 reveals a motor-actuated reel to which is anchored and around which is wound a flexible cable. One end of the cable is welded to a rod which is attached to the centermost of a concentric collection of coaxial interlocking tubular antenna sections. When the cable is unwound, the antenna is extended to the limit of the tubular interconnections and the drum is locked in place by clutch action against a gear. When the cable is wound, the antenna is collapsed so that each tube section is substantially within the next larger tube section. To fix the end of the antenna in this way necessarily requires that a relatively large volume be provided for the reel and for the motor, a requirement that is generally infeasible in relatively small devices, such as an expendable RF transmitter or receiver, with which the antenna might be used.
In the case of a coilable, self-erecting antenna element, such as the one described in the copending application "SELF-ERECTING COMPOSITE ANTENNA STRUCTURE" Ser. No. 399076 filed July 16, 1982, assigned to common assignee, use of a fixed ferrule requires the provision of a relatively large amount of space for bending the antenna element from coaxial alignment with the ferrule to an alignment perpendicular to the axis of the ferrule in order to coil the element about the device to which it is attached. Likewise, use of a reel would require provision of a relatively large volume for the reel that would reduce the advantages of such an antenna in space-limited applications. Thus both the fixed ferrule and the clutched drum methods of locking the position of the fixed end of a whip antenna suffer from the disadvantage of requiring more volume than is desirable for use in devices where space is a critical factor.